Engine misfires occur in internal combustion engines when the fuel fails to entirely combust. Misfires are undesirable because misfires reduce fuel efficiency and engine power output. In addition, misfires can also contribute to emission levels, as uncombusted fuel released to the atmosphere contains higher levels of particulate matter and Volatile Organic Compounds (“VOC”) than combusted fuel. As a result, regulatory agencies may seek to reduce emissions by controlling engines to reduce misfires.
Methods for detecting misfires are known, but false positives can result in undesired effects, such as reduced accuracy for detecting true positives and increased warranty expenses. These problems are aggravated by operating engines in environments known to create torsional vibrations that can deceptively appear to result from misfires. For example, vehicle operation in a ‘rough road’ environment can produce the apparently random torsional vibrations in a driveline that many misfire detection algorithms analyze. Furthermore, these rough road torsional vibrations of the driveline are characteristically low frequency, and therefore further mimic misfire effects on the driveline, further confounding many misfire detection algorithms.
False positive detection of misfire events can result in unnecessary warranty repair services as the false positive is recorded in an onboard log, and can illuminate a “check engine” light. Each of these outcomes can result in unnecessary services since the trigger (i.e. the misfire) did not occur.
Therefore, it would be desirable to provide a method and system of operating an engine that would overcome the aforementioned and other disadvantages.